<p>This work described a failure analysis report on the corrosion of downhole N80 tubing in a shale gas field in the Sichuan Basin, in order to determine the type of corrosion failure and the cause of failure of N80 tubulars, while the corresponding corrosion protection recommendations is also given. Through macroscopic observation and analysis of tubulars, in situ inspection of downhole pipelines, analysis of transport medium, inspection of chemical composition of failed tubulars, metallographic and organizational analysis of failed tubing, analysis of physical components of corrosion products, microscopic observation and analysis of surface elements and other testing of corrosion products, etc., the causes of corrosion failure and corrosion mechanism of materials are inferred and verified. The main contents include: relying on macro-observation analysis and in situ testing of oil well pipe to determine the failure area of the material, analyzing the composition of the transported fluid medium to predict the potential corrosion factors, measuring whether the applied oil well pipe meets the standard requirements via chemical composition testing and metallurgical organization analysis, and deducing the type of corrosion through the chemical composition and morphology analysis of corrosion products, and then inferring the reason and mechanism of corrosion failure. By analyzing the causes of corrosion failure of oil pipe, we speculate that the cause of corrosion is mainly the synergistic effect of carbon dioxide and corrosive microorganisms such as SRB, resulting in obvious corrosion perforations in the tubing. Therefore, we suggest that downhole tubulars should be protected from corrosion during shale gas field extraction to reduce the possibility of corrosion.</p>